Hook for attaching to a corporeal lumen and method of manufacturing

ABSTRACT

An improved hook provides for the attaching of endoluminal prosthesis within corporeal lumens. The hook is integrally formed with framing structure and is preset into an outward bend, but is resiliently flexible so as to form a substantially straight profile when compressed. The hook is capable of impinging upon the corporeal lumen and thereby securing the prosthesis. The hook may be configured for intraluminal delivery and deployment. A novel method of manufacturing said hook is also provided.

BACKGROUND OF THE INVENTION

This invention relates to an attachment element for fixation tocorporeal tissue and a method of manufacturing the same. Such anattachment element may be used to attach endoluminal prosthesis withinarteries, veins and similar lumens. As such, the attachment elementwould be capable of intraluminal delivery.

A variety of endoluminal prosthesis currently exist which requirefixation within corporeal lumens. Examples of such are grafts andstents. Grafts are artificial lumens which replace the natural lumen orreside within the natural lumen and isolate the natural tissue fromblood flow.

Stents are semi-rigid tubular structures which may be used to maintainthe patency of natural lumens or grafts. By providing scaffolding forthe lumen, stents prevent collapse and occlusion. Stents are typicallyformed either by winding wire into a tubular structure or removingmaterial from a solid tube.

Prior art grafts and stents have described the use of hooks to improvefixation of the prosthesis. These hooks were typically formed of bentwire attached to the prosthesis. The prior art also teaches integrallyformed hooks on the prosthesis. These integral hooks are formed to beaxially aligned with the prosthesis prior to deployment and forcedoutwardly upon intraluminal deployment.

What has not been taught by the prior art and was heretofore unknown isan integrally-formed, outwardly predisposed hook for attaching to acorporeal lumen. The present invention satisfies that need.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention embodies anattachment or anchoring element (ie., protrusion, hook, barb) forfastening to corporeal tissues and a method of manufacturing the same.The attachment or anchoring element is formed as an integral portion ofa metallic frame and has a preset outward bend or curve. The attachmentor anchoring element is generally comprised of an elongated member and apointed end. The pointed end is configured to impinge upon and possiblypierce corporeal tissue, plaque or other debris or disease.

In general, the present invention provides an improved attachment oranchoring element (which will be referred to herein as a hook forconvenience) for fixation of endoluminal prosthesis. As such, the hookis configured for intraluminal delivery within a catheter or capsule.The hook and endoluminal prosthesis may then be delivered to a diseasedor damaged portion of a corporeal lumen such as an artery or vein. Oncedelivered the hook may be compressed into or pierce the interior surfaceof the lumen. When compressed in such a fashion, the hook and prosthesisare securely fastened to the corporeal lumen.

There exists a variety of endoluminal prostheses which would benefitfrom the superior fixation provided by a hook which embodies thefeatures of the present invention. Once such device, an abdominal aorticgraft is used to treat abdominal aortic aneurysms. Such treatmentrequires the intraluminal delivery of the graft across the aneurysm.Once delivered the graft must be firmly attached to the surroundingtissue of the abdominal aorta. The present invention, in one possibleembodiment, may be configured to provide secure leak-proof fixation forabdominal aortic grafts.

The hook may be formed integrally with the endoluminal prosthesis to besecured. It may also be formed separately and attached to the prosthesisby a variety of well-known means. The hook is typically formed from ametallic frame. This frame could be separate from the host prosthesis orbe a portion thereof.

The hook is formed by cutting narrow incisions in the frame. Theseincisions define the elongated member and the pointed end. Laser-cuttingis a well-known method of making such incisions. Once the hook is cut itcan be bent outwardly such that the pointed end faces the direction inwhich the corporeal tissue will lie. This bend or curve in the hook maybe permanently set by heating. Once set, the hook may be pressed backinto the frame and the hook will spring back into the bent position whenreleased due to its resilient nature.

There are a variety of configurations for the hook which are embodied inthe present invention. The elongated member may have a constantcrosssection throughout its length. It may also have a reducingcross-section near the pointed end. The pointed end may include one ormore barbs. One configuration includes a single barb on either side ofthe pointed end, forming an arrowhead configuration. The pointed end mayalso be sharpened to further ensure fixation. Multiple hooks may beformed within a single frame. It is possible to form multiple hooks froma single set of incisions. Multiple hooks in opposing directions mayprovide superior fixation.

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the hook and frame.

FIG. 2 is a side view of the hook and frame piercing a corporeal lumenwall.

FIG. 3 is a side view of the hook and frame with the hook compressed.

FIG. 4 is a partial front view of multiple hook and frame combinationsformed integrally with a typical endoluminal prosthesis.

FIG. 5 is a perspective view of multiple hook and frame combinationsattached to a typical endoluminal prosthesis.

FIG. 6 is a perspective view of an endoprosthesis having medial hooks.

FIG. 7A is a front view of a first embodiment of the hook and frame.

FIG. 7B is a front view of a second embodiment of the hook and frame.

FIG. 7C is a front view of a third embodiment of the hook and frame.

FIG. 7D is a front view of a fourth embodiment of the hook and frame.

FIG. 7E is a front view of a fifth embodiment having multiple hooks on asingle frame.

FIG. 8 is a perspective view of a first embodiment of a mandrel assemblyfor bending the hook.

FIG. 9 is a partial cross-sectional view of a second embodiment of themandrel assembly and a hook and frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1 and 2, the invention may be embodied as a hook 20formed integrally within a frame 22. The hook 20 is comprised of anelongated member 24 and a pointed end 26. The hook 20 may be bent orcurved such that the pointed end 26 extends out of the frame 22.

The hook 20 and frame 22 are configured to secure themselves tocorporeal tissue. The pointed end 26 may be compressed onto corporealtissue such that it impinges into or possibly pierces the tissue. Withthe curve as shown in FIG. 2, force applied downward on the frame 22causes the hook 20 to embed into the tissue. A preferred configurationis sized to be delivered intraluminally and attach to the inside of ablood vessel. Another possibility is to configure the hook 20 and frame22 to attach to an artificial lumen such as an endoluminal graft.

In the compressed configuration, as depicted in FIG. 3, the hook 20 ispreferably compressed until the hook 20 is within the bounds orcircumference of the frame 22. In this manner, the combination of thehook 20 and frame 22 forms a nearly flat profile. Since the hook 20 hasbeen deformed into a preset bend, the pointed end 26 may still extend ashort distance out from the frame 22. Furthermore, due to the presetbend, the elongated member 24 may extend a short distance out of theframe 22 in the opposite direction from the pointed end 26. Thiscompression of the hook 20 provides a very narrow cross section whichfacilitates loading the device into a catheter for delivery.

The hook 20 and frame 22 may be attached to or formed as part of anintraluminal endoprosthesis 28. This configuration is depicted in FIG.4. When so attached, the function of the hook 20 and frame 22 is tosecure the endoprosthesis 28 within a vascular lumen. This may beaccomplished by forming or attaching the frame 22 on the endoprosthesissuch that the hook 20 will embed itself into the lumen when theendoprosthesis 28 is deployed. It is to be recognized that although FIG.4 shows hooks 20 configured at a superior end of the endoprosthesis 28,hooks 20 can also be incorporated into an inferior end of the device.

The hook 20 and frame 22 may also form part of an attachment device 29for a graft 30. This configuration is shown in FIG. 5. Such anarrangement may be attached to a superior end as well as inferior ends(not shown) of the graft 30. Additionally, the attachment device 29 maybe affixed longitudinally separated from the graft 30 or may be attachedto inside or outside surfaces thereof. The attachment device 29 expandsthe hook 20 into the vessel wall. The combined attachment forces of theimbedded hook 20 and the expanded attachment system 29 provide stablefixation of the endoluminal graft 30 within the vessel.

There exists a variety of devices that fit within the definitions of anintraluminal endoprosthesis 28 and a graft 30. Most of theses deviceswould benefit from the use of the securing devices defined herein. Asshown, the same may form part of grafts which primarily replace thenatural lumens or isolate them from the blood flow. Stents, whichprimarily ensure the patency of a lumen by resisting collapse andocclusion, can also benefit from the present invention as wouldimplantable blood clot filters such as those often put in the vena cava.

The addition of the frame 22 and hook 20 of the present invention toexisting grafts, stents and filters would provide such devices withsuperior fixation capability. For grafts the present invention willprovide the additional benefit of leak-proof sealing of the graft to theblood vessel.

Endoluminal devices are typically collapsed for intraluminal delivery.Upon delivery to the desired location within the corporeal lumen, thesedevices are re-expanded. This re-expanding is accomplished in a numberof ways. Balloon expansion requires the use of an angioplasty-typeballoon catheter, which expands a device located about the balloon.Self-expansion uses the spring forces or super-elastic properties of thecompressed device to expand outwardly once released. Shape memory metalshave also been used in endoluminal devices to expand upon the additionof energy or chemicals. The expansion forces of any of these methods aresufficient to embed the appropriately placed hook 20 into a corporeallumen. The frame 22 and hook 20 may be attached to the device such thatthe hook 20 is disposed radially outwardly from the device. As thedevice further expands radially outwardly the hook 20 is driven into thetissue of the corporeal lumen. Using several hook 20 and frame 22combinations around the perimeter of the device ensures the most secureattachment.

Another method of securing the hook 20 allows attachment without relyingupon expansion forces. The hook 20 may be impinged into the corporeallumen by translating the hook 20 and frame 22 axially. Since theelongated member 24 is bent outward as it extends toward the pointed end26, translating the hook 20 in the opposite direction of the elongatedmember's extension will force the pointed end 26 deeper into thecorporeal lumen. Implanting the hook 20 and frame 22 in a position suchthat the axial forces of the blood flow are in this same direction willhelp secure the device over an extended period.

The frame 22 may be a separate device or may be a portion of theendoluminal device to which the hook 20 and frame 22 are a part. Theframe 22 may be a small flat plate. Additionally since many endoluminaldevices are formed from tubes, the frame 22 may be a portion thereofthat is, the frame 22 may be curved. Within the FIG. the frame 22 isdepicted as a small roughly rectangular element with a connection 36 atone end. However, the frame 22 may be of any size or shape, or the frame22 may be indistinguishable from the components of the endoluminaldevice from which the frame 22 is formed.

The hook 20 and frame 22 are typically formed of metal. Biocompatiblestainless steel and Nitinol (Nickel Titanium Alloy), are particularlysuited for this purpose. More exotic materials such as ceramics andplastics may also perform adequately.

The hook 20 may be formed in the frame 22 by first cutting incisions 40into the frame 22. Preferably these incisions 40 are cut in such amanner as to remove the smallest amount of material from the frame 22and hook 20, while still allowing for stress relief and freedom ofmovement of the hook. This preferred method leaves the hook 20 boundedon three sides by a narrow incision 40. This cutting forms the elongatedmember 24 and the pointed end 26. Laser cutting is a process known inthe art which is preferred for making these incisions. To relieve thestresses caused by bending, additional material may be removed at theend of the incisions 40 in the form of cut-outs 52 (shown in FIG. 1).

With reference to FIG. 6, it is to be noted that it is also contemplatedthat an endoprosthesis 28 of the present invention can embody hooks 20that are located medial the ends 29, 31 of the endoprosthesis 28. Insuch an arrangement, the hooks 20 can be positioned at a junction 33between adjacent struts of adjacent cells 35 that define theendoprosthesis 28. It is to be recognized that although FIG. 9 shows ahook 20 positioned at each junction 33, for certain applications, fewerhooks 20 may be desirable.

Varying the configurations of the incisions 40 made in the frame 22 willprovide a variety of configurations of the hook 20. As depicted in FIG.7A the simplest configuration may be to cut parallel incisions 40 with apointed end 26 which forms a constant cross-section elongated member 24with a simple point.

Another configuration depicted in FIG. 7B has non-parallel incisions 40which narrow towards the pointed end 26. This produces an elongatedmember with a cross-section which reduces toward the pointed end 26. Thereduction in cross-section allows a decreasing bend radius near thepointed end 26. In this manner the pointed end may be pointed outwardlymore towards the perpendicular which aids in impinging the corporealtissue.

Another configuration, depicted in FIG. 7C, includes barbs 38 on thepointed end 26. With two such barbs 38 the pointed end has an arrowheadconfiguration. These barbs 38 may help secure the hook within thecorporeal lumen.

Combining configurations, as depicted in FIG. 7D, produces a narrowingelongated member 24 with barbs 38. Such a configuration could combinethe advantages of a decreasing bend radius with that of a barbed pointedend 26.

Another configuration, depicted in FIG. 7E, creates a plurality of hooks20 from the same incisions 40. This could form hooks 20 which project inopposing directions. Such a configuration would provide superiorresistence to radial and axial loads from the corporeal lumen and bloodflow.

The pointed end 26 of each of these configurations may be sharpened toimprove its ability to pierce the corporeal lumen. Material may beremoved from either or both the lumen-facing or frame-facing sides ofthe pointed end 26 to produce a sharper point.

The preferred method of manufacturing the hook 20 and frame 22 includescutting the hook 20 out of the frame 22 using narrow incisions 40.Several methods of making such incisions 40 in metal are well known.Possible examples are laser cutter, photo-etching and chemical etching.

Once the hook 20 is cut into the frame 22, it may be bent away from theframe 22. This may be accomplished manually by using tweezers to forcethe pointed end 26 of the hook 20 away from the frame 22. If the hook 20and frame 22 are formed as part of an endoluminal device, the device maybe mounted on a mandel 42 with pins 44 or similar means to force thepointed end 25 of the hook 20 away from the frame 22.

As depicted in FIG. 8, the mandrel 42 is preferably configured as acylindrical shaft with pins 44 appropriately spaced about thecircumference of the shaft. A frame 22 may be pressed against the shaft46 such that a pin 44 forces the hook 20 outwardly. This configurationcan be maintained while the hook 20 is heat sent to be permanentlypredisposed with an outward curve. Another preferred configuration forthe mandrel, as depicted in FIG. 9, includes a cylindrical shaft 46, aconvex outer ring 48 and a concave outer ring 50. A curved gap betweenthe outer rings forces the hook 20 into a predetermined bend. Thisconfiguration of shaft and rings may be clamped together for heatsetting.

After bending, the hook 20 may be permanently deformed into the curvedconfiguration by heat setting the material. For a Nitinol hook 20 andframe 22 combination heating at 550° C. for ten minutes is sufficient. Aceramic or plastic hook 20 and frame 22 combination might be formed in abent configuration.

With a permanently deformed hook 20, the hook 20 may still be compressedinto alignment with the frame 22 without losing the preset curve. Thus,the hook 20 may be compressed into the frame for intraluminal lowprofile delivery, and then deployed in the curved configuration byreleasing. This is a significant advantage in producing a fixationdevice small enough to be delivered intraluminally.

It will be apparent from the foregoing that, while particular forms ofthe invention have been illustrated and described, various modificationscan be made without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

What is claimed is:
 1. An endoprosthesis for use within a corporeal lumen, comprising: a graft; a frame element with incisions formed therein attached to the graft; the incisions forming an elongated member having a pointed end; and the elongated member bent away from said frame element, the elongate member having a permanent constant radius curve.
 2. The endoprosthesis of claim 1, wherein the elongated member has parallel straight sides defining a constant width.
 3. The endoprosthesis of claim 1, wherein the elongated member has non-parallel straight sides defining a narrowing width towards the pointed end.
 4. The endoprosthesis of claim 1, wherein the elongated member is resilient so as to be compressed into a position within the circumference of the frame element when constrained and to extend outside the circumference of the frame element when unconstrained.
 5. The endoprosthesis of claim 1, wherein the pointed end includes at least one barb.
 6. The endoprosthesis of claim 1, wherein the pointed end is sharpened.
 7. The endoprosthesis of claim 1, wherein the endoprosthesis is integrally formed into an endoluminal prosthesis.
 8. The endoprosthesis of claim 1, wherein the frame element defines a cylinder.
 9. The endoprosthesis of claim 8, wherein the cylinder is expandable radially without reliance upon relative movement of overlapping structure.
 10. A connector for fastening a device to corporeal tissues, said connector comprising: a hook having two sides and a point; said sides and said point defined by narrow slits in the connector; and said hook having a curve, the hook forming a permanent constant radius curve.
 11. The connector of claim 10, wherein the sides of the hook are parallel and straight and define a constant width.
 12. The connector of claim 10, wherein the sides of the hook are non-parallel and straight and define a narrowing width towards the point.
 13. The connector of claim 10, wherein the points is formed in an arrowhead configuration.
 14. The connector of claim 10, wherein the connector element defines a cylinder.
 15. The connector of claim 14, wherein the cylinder is expandable radially without reliance upon relative movement of overlapping structure.
 16. An endoluminal prosthesis, comprising: a frame element; and at least one protrusion cut out of said frame element having a resiliently flexible curve formed therein, the at least one protrusion forming a permanent constant radius curve.
 17. The endoluminal prosthesis of claim 16, wherein the frame element defines a cylinder.
 18. The endoluminal prostrhesis of claim 17, wherein the cylinder is expandable radially without reliance upon relative movement of overlapping structure.
 19. A method to manufacturing a hook for attaching to corporeal lumen, the hook being intergral with a frame element and predisposed outwardly therefrom, comprising the steps of: forming an elongate member in the frame element by cutting two sides and a pointed end; bending the elongate member such that the pointed end extends outwardly from the frame element; and heating the frame element and elongate member until the bend is permanently set.
 20. The method of claim 19, wherein the bending step further comprises compressing the frame element onto a mandrel having offset pins for bending the elongate members.
 21. The method of claim 19, further comprising the step of: sharpening the pointed end. 